Then pay for your own dedicated Internet access. Even if you do everything suggested, there's still plenty of opportunity for a man-in-the-middle attack by anyone in the complex or even within range of the complex's wireless signal. Odds are there won't be any kind of encryption on the signal if it's a public one, but even if there is, anyone in the complex will have to be given the password, so that would make life so much easier to crack any individual's network stream that they wished.
While the odds of someone doing a man in the middle type attack are probably pretty low, it's always a risk you will not be able to eliminate if you use the complex's wireless. If you pay for your own DSL or Cable service, that would be different. Then if you have a wireless signal for your apartment, you can set the encryption and encryption key, and not have to share it with anyone. Making it significantly harder for anyone to eavesdrop on your online activities. It still won't completely eliminate it, but you take the risk down from unlikely to very difficult.
If you're using a public wifi system, be it at an apartment complex, airport, coffee shop, whatever... You should assume that every action you take can and will be monitored by someone, no mater how many precautions you think you might be taking.